Conventionally, when collectively treating a large number of, for instance, wafers according to the plasma technique to produce semiconductor devices, it has been common to use a tray for transporting wafers. At that time, wafers or the like are simply placed on the tray or fixed thereto through the use of a holding or pressing jig or by the adhesion thereof to the tray with the use of, for instance, a sheet, a tape or grease, prior to subjecting them to a plasma treatment.
In this respect, it has been known that, when producing, for instance, a semiconductor device or a liquid crystal device and collectively treating a large number of waters or the like, the wafers or the like are fixed to a tray for transporting the same using a pressing means, and a tray composed of a protective substrate and a semiconductor substrate, serving as a tray for transportation, is conveyed, while it is set on an electrostatic chuck (see Patent Document 1 specified below).
It has also been known that semiconductor wafers or the like are processed, while they are held on a processing base by the adhesion of the same to the processing base through a foamed releasable sheet (see, for instance, Patent Document 2 specified below) or that a material to be processed such as a substrate is adhered to a processing base using a thermally releasable adhesive member such as a foamed releasable sheet (see, for instance, Patent Document 3 specified below).
The means for fixing a wafer onto a tray will hereunder be described, while referring to FIG. 1 which shows an example of the system for fixing a wafer to a tray through the use of a pressing jig as the pressing means described above and for simultaneously fixing the tray onto a processing stage using a mechanical clamping means.
Referring to FIG. 1, a tray-supporting stage 101 is provided with a plurality of or a number of flow paths 101a for allowing a heat-exchanging medium (such as helium (He) gas) to flow through the same. More specifically, the system for fixing a wafer to a tray as shown in FIG. 1 is so designed that a heat-exchanging medium introduced into the flow paths 101a first passes through the interior of the tray-supporting stage 101 and it is then supplied to the back face of a tray 102, which is placed on the tray-supporting stage 101, and simultaneously supplied to the back face of a wafer S to thus cool the tray 102 and the wafer S at the same time. The system for fixing a wafer to a tray as shown in FIG. 1 is likewise so designed that the marginal peripheral portion of the wafer S placed on the tray 102 is fixed onto the tray 102 by a holding or pressing jig 103 and the tray 102 is fixed onto the tray-supporting stage 101 by the action of a mechanical clamping member 104. In the case of this system, problems arise such that the fixation of the wafer S to the tray 102 requires much time, that the stability of the fixation of this type is insufficient in its reliability and that the effective areal region on the surface of the wafer S, which can be processed, is considerably reduced since the portion of the wafer S at the marginal periphery thereof, which comes in close contact with the pressing jig, cannot be subjected to the desired processing and, in other words, there are generated dead areas free of any processing at the portions used for holding or clamping the wafer.
Alternatively, another means for fixing a wafer onto a tray will hereunder be described, while referring to FIG. 2 which shows an example of the system for fixing a wafer to a tray by adhering the wafer to the tray through the use of an adhesive sheet such as the foregoing foamed releasable sheet and for simultaneously fixing the tray to a processing stage through the use of a mechanical clamp or an electrostatic chuck.
Referring now to FIG. 2, a tray-supporting stage 201 is provided with a plurality of or a number of flow paths 201a for allowing a heat-exchanging medium (such as helium (He) gas) to flow through the same. More specifically, the system for fixing a wafer to a tray as shown in FIG. 2 is so designed that a heat-exchanging medium introduced into the flow paths 201a can be supplied to the back face of the tray 202 mounted on the tray-supporting stage 201 to thus cool the tray 202. The system for fixing a wafer to a tray as shown in FIG. 2 is likewise so designed that the wafer S to be placed on the tray 202 is fixed onto the tray 202 through a heat-conductive adhesive sheet 204, while the tray 202 is fixed onto the tray-supporting stage 201 by a mechanical clamping member 203 or an electrostatic chuck means (not shown) which is embedded in the tray-supporting stage 201. In the case of this system, problems likewise arise such that the fixation of the wafer S to the tray requires much time, that the stability of the fixation of this type is insufficient in its reliability and that the system is inferior in the cooling efficiency.